30 ANALYSES OF ROCKS AND MINERALS, 1880-1908. 
B. Quartz porphyry, same locality. Alaskose. Analyzed for G. H. Williams, but 
never described. Analysis by L. G. Eakins, record No. 1350. 
C. Baltimore gneiss. Yellowstonose. Contains quartz, orthoclase, microcline, 
oligoclase, biotite, hornblende, magnetite, and minor accessories. P. R. C. 1701 
to 1705. 
D. Mica gneiss. III. 3.2. 8. Consists chiefly of quartz and muscovite, with feld- 
spars and minor accessories. P. R. C. 1707 to 1710. 
E. Hornblende gneiss. Auvergnose. Contains largely green hornblende and 
colorless anthophyllite, with plagioclase, magnetite, and scanty secondary quartz. 
P. R. €. 1710 to 1711. 
F. Hypersthene gabbro. Hessose. Contains quartz, orthoclase, labradorite, 
diallage, hypersthene, magnetite, apatite, and minor accessories. P. R. CO. 1712 to 
1714. 
Rocks ( to F are average samples collected by F. Bascom within the Philadelphia 
quadrangle. Analyses by W. F. Hillebrand, record No. 1872. The mica gneiss is 
described in the Cecil County volume of the Maryland Geological Survey. 
G. Sericite schist, Pine Grove Furnace, South Mountain. Collected by G. W. 
Stose. Analysis by W. T. Schaller, record No. 2302. 
Ka 
20 at 100° 
@ Loss on ignition. 
MARYLAND AND THE DISTRICT OF COLUMBIA. 
1, PERIDOTITE AND PYROXENITE. 
Rocks A to I, inclusive, described by G. H. Williams in Am. Geologist, vol. 6, p. 35. 
A. Porphyritic lherzolite, Johnny Cake road, Baltimore County. SR. 1 of baltt- 
moriase. Contains olivine, bronzite, and diallage, the olivine partly serpentinized. 
Analysis by T. M. Chatard, record No. 1094. 
B. Websterite, Johnny Cake road. Baltimorose. Consists entirely of hypersthene 
and diallage. P. R.C. 110, and 1740. 
C, D. Alterations of B. Maricose. B,C, and D dried at 104° P.R.C.1741. 
E. Smaragdite rock, altered pyroxenite, Dogwood road, Baltimore County. 
Cecilose. : 
Analyses B, C, D, and E by J. E. Whitfield, record Nos. 975, 976. ©, D, and E are 
from the laboratory record and do not appear in the published paper. 
